1. Field of the Invention
The present invention relates to an abrasive nozzle head of an abrasive water jet device which directs onto a workpiece an abrasive water jet obtained by mixing a abrasive into high pressure water.
2. Description of the Related Art
In the past, an abrasive water jet obtained by mixing a abrasive into high pressure water jet has been used to cut a workpiece or the like. A device for discharging such abrasive water jet is of a type in which high pressure water is jetted from an abrasive nozzle while passing from a water nozzle through a mixing chamber, thereby generating negative pressure in the mixing chamber, and taking the abrasive into the mixing chamber using the negative pressure, in order to discharge an abrasive water jet while mixing the abrasive into the high pressure water.
For example, as shown in FIG. 6, a common abrasive nozzle head 41 for use in the device of this type includes a hollow head body 42 that is mounted to a nozzle adapter 50 supplying high pressure water. The interior of the head body 42 includes: a water nozzle 43 that jets high pressure water; a mixer member 44 that is formed with a abrasive supply port 45 into which a abrasive is introduced, and a mixing chamber 46 for mixing the abrasive supplied from the supply port 45 into the high pressure water; and an abrasive nozzle 47 that discharges an abrasive water jet obtained by mixing the abrasive into the high pressure water, the water nozzle 43, the mixer member 44, and the abrasive nozzle 47 being arranged coaxially with the jet axis X of the water jet (see, for example, Japanese Unexamined Patent Application Publication No. Hei 6-328365 and U.S. Pat. No. 6,601,783).
The water nozzle 43, mixer member 44, abrasive nozzle 47 and the like are consumable components which wear out from use and need replacement. These consumable components are configured from components independent of one another for the purpose of appropriate replacement if necessary, and coaxially incorporated and fixed in the hollow head body.
Further, typically, as shown in FIG. 6, a side hole 48 exposing the abrasive supply port 45 is formed by drilling in a side surface of the head body. A abrasive supply hose 51 is connected to the head body through a hose adapter 52 inserted into the side hole 48, and communicates with the abrasive supply port 45.
However, the consumable components, which are incorporated in the head body and independent of one another, as described above, are of different replacement timings. For example, as for the service life of each consumable component which corresponds to the replacement interval, while the water nozzle has a relatively long life of 500 to 1000 hours, that of the abrasive nozzle is 70 to 100 hours; that of the mixer member is 150 to 300 hours; and that of the hose adapter is 150 to 300 hours. Although these service lives are reference values (because the water nozzle depends on ON/OFF times and the components other than the water nozzle depend on the amount of abrasive to be supplied), it is apparent that their service lives differ from one another. Therefore, in some cases, there has arisen a need for disassembling the whole abrasive head including other components which do not need to be replaced at the time of replacement of a component to be replaced.
For example, in the abrasive nozzle head 41 of FIG. 6, at the time of replacement of the mixer member 44, firstly by loosening each fixing nut 49 and removing the abrasive nozzle 47 from the head body 42, and then removing the head body 42 from the nozzle adapter 50, and also then, by removing the mixer member 44 from the head body 42, and removing the water nozzle 43 from the mixer member 44, the single mixer member 44 is removed from the abrasive nozzle head 41. Then, after mounting the water nozzle 43 to a new mixer member 44, the new mixer member 44 is attached to the head body 42, then the head body 42 is attached to the nozzle adapter 50, and then the previously-removed abrasive nozzles 47 are sequentially attached to the head body 42, thereby completing the replacement of the mixer member 44. In this manner, at least eight processes have been necessary for the replacement work of the mixer member 44.
Furthermore, in some abrasive nozzle heads of the related art, the water nozzle 43 is replaceably fitted and disposed in a recess that is formed on the upstream end side of the mixer member 44 as shown in FIG. 6. In this case, as described above, every time the mixer member 44 is replaced, the water nozzle 43 is also removed even if it does not need to be replaced. Although the service life of the water nozzle is typically several times longer than the mixer member, repetition of the removal work associated with the replacement of the mixer member could result in the early occurrence of seal failure in some sealing forms. Further, replacement of such water nozzle mounted to the mixer member is also performed by the procedure that requires the disassembly of the whole abrasive head.
As described above, in the abrasive nozzle head of the related art, it has taken troublesome labor and time to replace consumable components, particularly, the mixer member.
Accordingly, in view of the above-described problem, an object of the present invention is to provide an abrasive nozzle head which includes a configuration that makes the replacement of a mixer member easier than the related art.